1. Field of the Invention
The present invention relates to a control system for controlling the timing for making an electric spark in the engine of a vehicle.
2. Description of Related Art
There is the increasing tendency that engines, particularly engines for automobiles, are designed to retard the timing for sparking when the knocking of the engine is sensed by a knocking sensor.
Control of the ignition timing by using the knocking sensor is not sufficient to fully prevent the knocking because the control is implemented after the knocking has occurred. Hence, it has been proposed that the ignition timing be retarded in a predetermined amount in anticipation when a running state is sensed in which the knocking is likely to occur. Japanese Patent Unexamined Publication (Kokai) No. 138,164/1988 discloses the technique in which the ignition timing is retarded in a predetermined amount in advance at the time of acceleration when the knocking may readily occur. It is preferred that an amount of this retard be as small as possible within the range in which the knocking can be prevented, in order to impair accleration performance.
Recently, many vehicles are provided with at least a common engine and separate transmissions. In other words, it is common that the vehicle with automatic transmission loaded is distinguished from the vehicle with manual transmission loaded. It is in general that the automatic transmission is provided with a torque converter.
It has been found, however, that the vehicle with the torque converter disposed in the driving system of the engine is likely to cause knocking at the time of acceleration, as compared with the vehicle without the torque converter, when the retarding amount for the vehicle with the torque converter is set to a value which is the same as that for the vehicle with no torque converter.
As a result of review on the cause of this phenomenon, it has been found that the knocking is likely to occur because the operator has the growing tendency of depressing the accelerator pedal more by the amount of a slip of the torque converter when the operator intends to gain a feeling of acceleration to a similar extent.